How to Calculate Scope 2 Electricity Emissions in Australia

Scope 2 electricity emissions are the most common and most accessible emissions figure for most Australian businesses. Virtually every organisation that occupies a building consumes grid electricity, and that consumption produces indirect greenhouse gas emissions at the point of generation.

Calculating it correctly — and in a way that satisfies assurance requirements — requires understanding the two calculation methods and the specific factors to use.

The two methods: location-based and market-based

AASB S2 (and the underlying GHG Protocol Scope 2 Guidance) requires disclosure of Scope 2 electricity emissions using both methods:

Location-based method: Uses the average emission intensity of the electricity grid in the region where you consume electricity. For Australia, this means the state or territory grid factor from the NGA Factors published by DCCEEW.

Market-based method: Uses emission factors from contractual instruments (Power Purchase Agreements, GreenPower, Renewable Energy Certificates). If you haven’t entered into any such instruments, your market-based figure defaults to your location-based figure using a residual mix factor.

Both figures need to be disclosed. They serve different purposes:

• Location-based reflects the real-world impact of your consumption on the grid
• Market-based reflects the impact of your procurement decisions

Step 1: Get your consumption data

Your starting point is the electricity consumption figure from your invoice or meter read: kWh for the billing period.

Make sure you’re using actual reads, not estimated reads. Estimated reads are projections from the retailer — the actual consumption may differ, and the correction will appear on a later invoice.

For businesses with multiple sites or meters, collect consumption for each NMI (National Meter Identifier) separately, tagged with the site and billing period.

Step 2: Identify the relevant grid factor

Australia has several electricity grids with different emission intensities:

Grid	Approximate factor (FY2024, kg CO₂e/kWh)	Notes
Queensland (NEM)	~0.77	Declining as solar and gas grow
New South Wales (NEM)	~0.75	Similar declining trend
Victoria (NEM)	~0.94	Higher due to remaining brown coal
South Australia (NEM)	~0.31	Strong renewables penetration
Tasmania (NEM)	~0.11	Predominantly hydro
ACT (NEM)	~0.09	100% GreenPower procurement
Western Australia (SWIS)	~0.61	Isolated grid, gas-heavy
Northern Territory	~0.61	Isolated grid

Note: Use the current-year NGA Factors for accurate figures. The above are indicative only.

The grid factor to use is the one for the state or territory where the meter is located — not your corporate headquarters.

Step 3: Apply the location-based calculation

kWh × grid factor (kg CO₂e/kWh) = kg CO₂e

Convert to tonnes: ÷ 1,000

Example:

• Site in Victoria
• Consumption: 250,000 kWh for FY2025
• Grid factor (Victoria, NGA FY2025): 0.94 kg CO₂e/kWh
• Location-based Scope 2: 250,000 × 0.94 = 235,000 kg = 235 tonnes CO₂e

Step 4: Apply the market-based calculation

If you have no contractual instruments (no GreenPower, no PPA, no RECs), your market-based figure equals your location-based figure.

If you have GreenPower accreditation:

• GreenPower carries a zero-emission factor for the GreenPower component
• Calculate the non-GreenPower component using the residual mix factor (available from GreenPower or a sustainability adviser)
• Sum the two components

If you have a PPA (Power Purchase Agreement) for accredited renewable energy:

• The PPA-covered portion carries the contracted renewable factor (typically zero or close to zero)
• The remainder uses the residual mix factor or location-based factor depending on your accounting approach

Document the instruments you have in place: contract reference, volume covered, and the emission factor source.

Step 5: Record the methodology

For assurance purposes, record for each calculation:

• The NMI or meter reference the consumption relates to
• The billing period
• The consumption (kWh)
• Whether the read was actual or estimated
• The NGA Factors version used
• The specific grid factor and table reference
• Any contractual instruments affecting the market-based calculation
• The resulting CO₂e figure (both methods)

This record is the audit trail that allows your assurance provider to verify the calculation without having to reconstruct it from scratch.

Multi-site considerations

For organisations with many sites across multiple states, the calculation process scales as follows:

1. Aggregate consumption by NMI (one row per meter per billing period)
2. Map each NMI to its state/territory grid
3. Apply the relevant factor for each NMI
4. Sum to site level, then project level, then corporate level

The state mapping is important — a national retailer with sites in all states has a different grid factor for Sydney and Melbourne sites even if they’re with the same electricity retailer.

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Ayika handles the grid factor mapping and location-based calculation automatically, with NGA factor versioning built in so every figure is traceable. See how electricity data flows through the platform.